Thermal interface material and method of making and using the same

ABSTRACT

A thermal interface material comprises a polymeric elastomer material, a thermally conductive filler, and a coupling agent, along with other optional components. In one exemplary heat transfer material, a coupling agent having the formula: 
     
       
         
         
             
             
         
       
         
         
           
             where Y is either a cyclic structure or Y is represented by Formula II: 
           
         
       
    
     
       
         
         
             
             
         
       
         
         
           
             where: 
             a=1 or 2 
             b=2 or 3 
             R 1  contains at least one of a neoalkoxy group, an ether group, or a C2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, or alkaryl group 
             R′ 2  and R″ 2  are independently selected from Hydrogen, a neoalkoxy group, an ether group, and a C2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, or alkaryl group 
             X=Group four transition metal; and 
             where a=1, R 3  contains at least one of a neoalkoxy group, an ether group, or a C2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, or alkaryl group; or 
             where a=2, the two R 3  groups independently contain at least one of a neoalkoxy group, an ether group, or a C2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, or alkaryl groups or the two R 3  groups together form an alkyldiolato group 
             and, if Y is a cyclic structure, X is a member of the cyclic structure and the cyclic structure also contains a pyrophosphate group such as Formula II shown above.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national phase application of PCT/US2009/069090,filed Dec. 22, 2009, which claims priority to Provisional ApplicationNo. 61/156,733, filed Mar. 2, 2009. Both of these applications arehereby incorporated herein by reference in their entirety.

BACKGROUND

Electronic components are used in ever increasing numbers of consumerand commercial products. As consumer demand drives electronic devices tobecome smaller and operate at higher speeds, heat energy dissipated fromelectronic components in these devices increases dramatically. A commonpractice in the industry is to use thermal interface materials (TIMs)such as thermal grease, or grease-like materials, phase change materialsor elastomer tapes, alone or on a carrier in such devices to transferthe excess heat dissipated across physical interfaces. However, when theability of these materials to transfer heat breaks down, the performanceof the electronic device in which they are used may be adverselyaffected.

SUMMARY OF THE INVENTION

According to some embodiments of the present invention, a heat transfermaterial comprises a polymeric elastomer material, a wax, a thermallyconductive filler, an antioxidant, and a coupling agent.

In some embodiments, the coupling agent has the Formula I:

where Y is either a cyclic structure or Y is represented by Formula II:

where:

a=1 or 2

b=2 or 3

R₁ contains at least one of a neoalkoxy group, an ether group, or aC2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, oralkaryl group

R′₂ and R″₂ are independently selected from Hydrogen, a neoalkoxy group,an ether group, and a C2-C30 straight or branched alkyl, alkenyl,alkynyl, aralkyl, aryl, or alkaryl group

X=Group four transition metal; and

where a=1, R₃ contains at least one of a neoalkoxy group, an ethergroup, or a C2-C30 straight or branched alkyl, alkenyl, alkynyl,aralkyl, aryl, or alkaryl group; or

where a=2, the two R₃ groups independently contain at least one of aneoalkoxy group, an ether group, or a C2-C30 straight or branched alkyl,alkenyl, alkynyl, aralkyl, aryl, or alkaryl groups or the two R₃ groupstogether form an alkyldiolato group

and, if Y is a cyclic structure, X is a member of the cyclic structureand the cyclic structure also contains a pyrophosphate group such asFormula II shown above. For example, R₁ in Formula II may be absent andthe oxygen atom that is adjacent to R₁ is coupled directly or indirectlyto X.

Also disclosed are electronic subassemblies and electronic devices inwhich the heat transfer material is incorporated, along with methods formanufacturing heat transfer materials and methods for using heattransfer materials.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional view of an electronic assembly accordingto some embodiments of the present invention.

While the invention is amenable to various modifications and alternativeforms, specific embodiments have been shown by way of example in thedrawings and are described in detail below. The intention, however, isnot to limit the invention to the particular embodiments described. Onthe contrary, the invention is intended to cover all modifications,equivalents, and alternatives falling within the scope of the inventionas defined by the appended claims.

DETAILED DESCRIPTION

Thermal interface materials are used in a wide variety of electronicdevices. For example, electronic devices that include one or moresemiconductor dies may use a thermal interface material in order tofacilitate the removal of heat from the one or more semiconductor dies.

FIG. 1 shows an electronic assembly 1, which may be subsequentlyintegrated into an electronic device and sold as a part of theelectronic device. The assembly 1 includes a semiconductor die orprocessor 10, a heat spreader 12, and a thermal interface material(TIM1) 14 disposed between the semiconductor die 10 and the heatspreader 12. As shown, the TIM1 14 contacts at least a portion of thesurface of both the semiconductor die 10 and the heat spreader 12,providing a physical interface through which thermal energy can betransmitted. As discussed in more detail below, the TIM1 14 can beformulated to maximize the contact area between the TIM1 14 and thesemiconductor die 10 and between the TIM1 14 and the heat spreader 12.This contact area facilitates heat transfer from the semiconductor die10 through the TIM1 14 and the heat spreader 12 to the surroundingenvironment. The surrounding environment may be air or any other gaswithin or around an electronic device, or another solid or non-solidmaterial.

FIG. 1 also shows a thermal interface material (TIM2) 16 in contact withthe heat spreader 12. The TIM2 16 may be disposed over the heat spreader12 and may provide for increased heat transfer from the heat spreader 12to a heat sink (not shown). The TIM2 16 may be formulated to maximizethe contact area between the TIM2 16 and the heat spreader 12 andbetween the TIM2 16 and the heat sink. This contact area facilitatesheat transfer from the heat spreader 12 through the TIM2 16 and the heatsink to the surrounding environment. In such an embodiment, the TIM2 16may contact at least a portion of the surface of both the heat spreader12 and the heat sink, providing a physical interface through whichthermal energy can be transmitted. The heat sink may facilitate thetransfer or thermal energy to the surrounding environment and/orfacilitate the storage of thermal energy. The surrounding environmentmay be air or any other gas within or around an electronic device, oranother solid or non-solid material in contact with the TIM2 16 (e.g.,the heat sink). While FIG. 1 shows both the TIM1 and the TIM2, in somealternative embodiments only a TIM1 may be used and the TIM2 omitted.

In yet other embodiments, a heat sink may be disposed over the die orprocessor and a thermal interface material may be disposed between thedie or processor and heat sink (in such embodiments the heat spreader 12may be omitted). This configuration is often referred to as a TIM1.5application. In such an embodiment, the TIM1.5 may contact at least aportion of the surface of both the die or processor and the heat sink,providing a physical interface through which thermal energy can betransmitted. The heat sink may facilitate the transfer or thermal energyto the surrounding environment and/or facilitate the storage of thermalenergy.

In some embodiments the TIM1 and TIM2 materials may comprise the samematerial, while in other embodiments the TIM1 and TIM2 materialscomprise different materials. For example, any of the thermal interfacematerials described herein may be used as a TIM1, a TIM2, both a TIM1and TIM2, or as a TIM1.5.

The thermal interface material includes a heat transfer material thatgenerally comprises a polymeric elastomer material, a thermallyconductive filler, and a coupling agent, along with other optionalcomponents. In one embodiment, the thermal interface material maycomprise a polymeric elastomer material, a wax, a thermally conductivefiller, an antioxidant and a coupling agent.

The coupling agent is an organometallic compound.

In some embodiments, the coupling agent may be represented by Formula I:

where Y is either a cyclic structure or Y is represented by Formula II:

where:

a=1 or 2

b=2 or 3

R₁ contains at least one of a neoalkoxy group, an ether group, or aC2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, oralkaryl group

R′₂ and R″₂ are independently selected from Hydrogen, a neoalkoxy group,an ether group, and a C2-C30 straight or branched alkyl, alkenyl,alkynyl, aralkyl, aryl, or alkaryl group

X=Group four transition metal; and

where a=1, R₃ contains at least one of a neoalkoxy group, an ethergroup, or a C2-C30 straight or branched alkyl, alkenyl, alkynyl,aralkyl, aryl, or alkaryl group; or

where a=2, the two R₃ groups independently contain at least one of aneoalkoxy group, an ether group, or a C2-C30 straight or branched alkyl,alkenyl, alkynyl, aralkyl, aryl, or alkaryl groups or the two R₃ groupstogether form an alkyldiolato group

and, where Y is a cyclic structure, X may be a member of the cyclicstructure and the cyclic structure may also contain a heteroatom group,for example a pyrophosphate group such as Formula II shown above, or anyof the other heteroatoms described herein. For example, in someembodiments R₁ in Formula II may be absent and the oxygen atom that isadjacent to R₁ is coupled directly or indirectly to X. As one example ofsuch a cyclic structure that contains a pyrophosphate heteroatom group,see Formula IX below.

For example, in some embodiments, the coupling agent may be representedby the Formula III:

where:

c=1 or 2

d=2 or 3

R₄ contains at least one of a neoalkoxy group, an ether group, or aC2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, oralkaryl group

R₅ contains at least one of a neoalkoxy group, an ether group, or aC2-C30 straight or branched alkyl, alkenyl, alkynyl, aralkyl, aryl, oralkaryl group

X=Group four transition metal; and

where c=1, R₆ contains at least one of a neoalkoxy group, an ethergroup, or a C2-C30 straight or branched alkyl, alkenyl, alkynyl,aralkyl, aryl, or alkaryl group; or

where c=2, the two R₆ groups independently contain at least one of aneoalkoxy group, an ether group, or a C2-C30 straight or branched alkyl,alkenyl, alkynyl, aralkyl, aryl, or alkaryl groups or the two R₆ groupstogether form an alkyldiolato group.

In some embodiments, the coupling agent includes one or more titaniumatoms, zirconium atoms, or other suitable Group four transition metal.In some such embodiments, the metal has at least one heteroatomfunctional group attached to the metal atom, for example a pyrophosphatefunctional group. Examples of suitable pyrophosphate groups aredescribed in U.S. Pat. No. 4,634,785, filed Sep. 14, 1984, entitled“Titanium and Zirconium Pyrophosphates, their Preparation and Use”; andU.S. Pat. No. 4,122,062, filed Sep. 30, 1975, entitled “Alkoxy TitanateSalts Useful as Coupling Agents”, both of which are herein incorporatedby reference in their entirety. In some embodiments, the coupling agenthas one, two or three such heteroatom functional groups attached to themetal atom. Each of the heteroatom functional groups may comprise one ormore or two or more heteroatoms (e.g., one, two, or two or more,phosphate atoms), and the one or more heteroatoms may each have a numberof oxygen atoms bonded thereto (in some cases, an oxygen atom may alsobe disposed between, and bonded directly to, two of the heteroatoms).Further, in some embodiments at least one of the heteroatoms may haveone or more hydroxyl groups bonded thereto. One exemplary heteroatomfunctional group comprises a pyrophosphate functional group with atleast one hydroxyl group attached to one of the phosphate atoms.

In addition, each of the one or more heteroatom functional groups mayhave one or more organic groups attached to the heteroatom functionalgroup (e.g., see the —OR₁, —OR′₂, —OR″₂, —OR₄, and OR₅ groups in theabove formulas). As described above, the R₁, R′₂, R″₂, R₄, and R₅ groupsmay contain neoalkoxy groups, ether groups, and/or straight or branchedalkyl, alkenyl, alkynyl, aralkyl, aryl, or alkaryl group groups. The R₁,R′₂, R″₂, R₄, and R₅ groups may have from 2 to 30 carbon atoms, from 6to 24 carbon atoms, from 8 to 24 carbon atoms, or from 8 to 16 carbonatoms. In some embodiments in which two or more organic groups areattached to a heteroatom functional group, the organic groups on a givenheteroatom are the same, while in other embodiments the organic groupsmay differ from one another. As one example, one or more of the organicgroups may be an alkyl group attached to the oxygen, togetherrepresenting an alkylether group such as an octylether group (e.g., seeFormulas IV through IX, shown below), and each heteroatom functionalgroup may have two octylether groups attached thereto.

The metallic atom of the organometallic compound may also have one ortwo organic groups attached directly thereto (for example, see the R₃O—or R₆O— groups in Formulas I and III). For example, the one or moreorganic groups attached to the metallic atom may contain a neoalkoxygroup, an ether group, and/or the R₃ or R₆ group may contain a C2-C30,C6-C24, C8-C24, or C8-C16 straight or branched alkyl, alkenyl, alkynyl,aralkyl, aryl, alkaryl group.

A neoalkoxy group is a branched organic functional group that in someembodiments may have the formula (R₇)(R₈)(R₉)CCH₂O—, where the R₇, R₈and R₉ are each a monovalent alkyl, alkenyl, alkynyl, aralkyl, aryl, oralkaryl group, a halogen, an ether substituted derivative thereof, anoxy derivative or an ether substituted oxy derivative of any of thesegroups. Specific examples of such organic functional groups that may beattached directly to the metallic atom or a heteroatom group include 2,2(bis 2-propenolatomethyl)butanolato and 2-propanolato. Additionalexamples of neoalkoxy functional groups are provided in U.S. Pat. No.4,600,789, filed May 14, 1984, entitled “Neoalkoxy Organo-TitanateUseful as Coupling and Polymer Processing Agents”; U.S. Pat. No.4,623,738, filed Apr. 22, 1985, entitled “Neoalkoxy Organo-Titanates andOrgano-Zirconates Useful as Coupling and Polymer Processing Agents”; andU.S. Pat. No. 4,657,988, filed Feb. 28, 1986, entitled“Repolymerization.” All of these patents are herein expresslyincorporated by reference in their entirety.

As mentioned above, in some embodiments in which a=2 or c=2, the twoR₃O— or R₆O— groups may be joined together, in some embodiments forminga diolato structure, for example an alkyldiolato group (e.g., see thestructures shown below in chemical formulas (IV) and (VIII)). Thealkyldiolato may be an oxoalkyldiolato or a dioxoalkyldiolato. Thealkydiolato groups may also comprise side chains comprising additionalorganic functional groups. Examples of diolato groups that may beincluded as the R₃O— or R₆O— groups are provided in U.S. Pat. No.4,087,402, filed Apr. 19, 1976, entitled “Organo-Titanate Chelates andTheir Uses”; and U.S. Pat. No. 4,277,415, filed Aug. 29, 1979, entitled“Pyrophosphato Titanate Adducts,” both of which are incorporated byreference herein in their entirety.

Following are some examples of coupling agents that may be used in thepresent invention:

Zirconium IV 2,2 (bis 2-propenolatomethyl)butanolato,tris(diisooctyl)pyrophosphato-O:

Titanium IV bis(dioctyl)pyrophosphato-O, ethylenediolato (adduct),bis(dioctyl)hydrogen phosphite:

Titanium IV, 2-propanolato, tris(dioctyl)-pyrophosphato-O) adduct with 1mole of diisooctyl phosphite:

Titanium IV 2,2 (bis 2-propenolatomethyl)butanolato,tris(dioctyl)pyrophosphato-O:

Titanium IV bis(dioctyl)pyrophosphato-O, oxoethylenediolato, (adduct),bis(dioctyl) (hydrogen)phosphite:

(Zirconium IV 2,2-bis(2-propenolatomethyl)butanolato, cyclo di[2,2-(bis2-propenolatomethyl)butanolato], pyrophosphato-O,O):

The heat transfer material may include any one of the coupling agentsgenerally or specifically described above, or any combination thereof.The heat transfer material may comprise from about 0.1 wt % to about 3wt %, from about 0.30 wt % to about 2.0 wt %, or from about 0.50 wt % toabout 1.0 wt %, of coupling agent.

In some embodiments, the polymeric elastomeric component is a siliconerubber, a siloxane rubber, a siloxane copolymer or any other suitablesilicone-containing rubber. In other embodiments, the polymericelastomeric component is a hydrocarbon rubber compound or a blend ofrubber compounds. The hydrocarbon rubbers may comprise saturated orunsaturated rubber compounds. In some embodiments, saturated rubbers maybe used and may be less sensitive to thermal oxidation degradation.Examples of saturated rubbers that may be used in accordance with theinvention are ethylene-propylene rubbers (EPR, EPDM),polyethylene/butylene, polyethylene-butylene-styrene,polyethylene-propylene-styrene, hydrogenated polyalkyldiene “mono-ols”(such as hydrogenated polybutadiene mono-ol, hydrogenated polypropadienemono-ol, hydrogenated polypentadiene mono-ol), hydrogenatedpolyalkyldiene “diols” (such as hydrogenated polybutadiene diol,hydrogenated polypropadiene diol, hydrogenated polypentadiene diol) andhydrogenated polyisoprene, polyolefin elastomer, or any other suitablesaturated rubber, or blends thereof. In some embodiments, a hydrogenatedpolybutadiene mono-ol may be used, and in some cases is referred to as ahydroxyl-terminated ethylene butylene copolymer, specialty mono-ol.

In other embodiments, unsaturated rubbers may be used. Examples ofunsaturated rubbers and rubber compounds are polybutadiene,polyisoprene, polystyrene-butadiene and other suitable unsaturatedrubbers, blends thereof, or blends of saturated and unsaturated rubbercompounds. If the rubber is unsaturated, in some embodiments thecompound may undergo a hydrogenation process to rupture or remove atleast some of the double bonds. As used herein, the phrase“hydrogenation process” means that an unsaturated organic compound isreacted with hydrogen by either a direct addition of hydrogen to some orall of the double bonds, resulting in a saturated product (additionhydrogenation), or by rupturing the double bond entirely, whereby thefragments further react with hydrogen (hydrogenolysis).

The rubber compounds may be “self-crosslinkable” in that they couldcrosslink intermolecularly with other rubber molecules orintramolecularly with themselves, depending on the other components ofthe composition. The intramolecular and intermolecular cross-linkingwith the rubber compounds may be facilitated by optional cross-linkingagents, as discussed further below.

The heat transfer material may comprise from about 1 wt % to about 50 wt%, or from about 3 wt % to about 14 wt %, or from about 5 wt % to about10 wt %, of polymeric elastomer material.

The thermally conductive filler materials may comprise thermal fillerparticles that are dispersed in the heat transfer material. The thermalfiller particles generally have a high thermal conductivity. Suitablefiller materials include silver, aluminum, copper and alloys thereof,boron nitride, aluminum nitride, silver coated copper, silver coatedaluminum, carbon fiber, and metal coated carbon fiber such as nickelcoated fiber. Typical filler average particle sizes may be in the rangebetween about 0.5 and about 25 μm, between about 1 μm and about 25 μm,or between about 2 μm and about 20 μm, with a maximum particle size ofabout 100 μm. The particle size distribution of the filler particles maybe a unimodal distribution or a mutilmodal (e.g., bimodal or trimodal)distribution. Dispersion of filler particles within the polymericelastomer material may be facilitated by addition of the coupling agentsdescribed above. The heat transfer material may comprise between about30 wt % and about 99 wt %, from about 80 wt % to about 95 wt %, or fromabout 85 wt % to about 92 wt %, of thermal filler material.

In addition, the heat transfer material may also have an optional wax orphase change material. For some applications such as land grid array(LGA) applications, the waxes or phase change materials may have amelting point of less than about 90° C., between about 40° C. and about90° C., between about 45° C. and about 70° C., or between about 45° C.and about 60° C. For other applications such as ball grid array (BGA),high temperature LGA, or non-LGA applications, the waxes or phase changematerials may have a melting point of less than about 165° C., less thanabout 110° C., between about 40° C. and about 165° C., between about 45°C. and about 110° C., or between about 45° C. and about 60° C.

The heat transfer material may comprise less than about 30 wt %, lessthan about 10 wt %, or from about 1 wt % to about 5 wt %, of wax orother phase change material. The wax or phase change component of theheat transfer material may comprise paraffin waxes (i.e.,microcrystalline paraffin waxes), polymer waxes or natural waxes, or anycombination thereof. Paraffin waxes are a mixture of solid hydrocarbonshaving a general formula C_(n)H_(2n+2), having melting points in therange of about 20° C. to about 100° C. Typically polymer waxes arepolyethylene waxes, polypropylene waxes, or copolymers (e.g.,ethylene-maleic anhydride or ethylene-vinyl acetate, or othercopolymers), and have a range of melting points from about 40° C. toabout 165° C., or about 140° C. or less. Natural waxes include carnaubawax (melting point between about 82° C. and about 86° C.) and bees wax(melting point between about 62° C. and about 64° C.).

The wax or phase change component may allow the heat transfer materialto have a melting point or a melting point range that is at or below theoperating temperature of the electronic device in which the heattransfer material will be used. As such, the heat transfer material maysoften or melt under normal operating conditions, allowing the heattransfer material to flow across, and better conform to, any surfacesthrough which heat transfer is desired. This softening and/or flowingacross the heat transfer surfaces may facilitate the efficient transferof heat between the components of an electronic device. In someembodiments, the heat transfer material may start melting at about 40°C., about 45° C., about 90° C., or about 100° C., or may partially orentirely melt between about 40° C. to about 90° C., between about 45° C.and about 85° C., between about 45° C. and about 50° C., or betweenabout 100° C. and about 115° C.

The wax or phase change material is an optional component. In someembodiments the polymeric elastomer material and/or the filler materialand/or an additional component of the heat transfer material may have aphase change within the normal operating temperatures of the electronicdevice in which the heat transfer material is used. As a result, thepolymeric elastomer and/or the filler and/or the additional component ofthe heat transfer material may facilitate the softening of the heattransfer material during normal operating conditions in order to allowfor the heat transfer material to flow across, and better conform to,any surfaces through which heat transfer is desired.

Optional additional components may comprise an oil, such as an α-olefincopolymer, an ethylene-propylene copolymer, a paraffinic oil or othernon-crystalline aliphatic material. As one example, an oil may be used,which may also be described as a hydrocarbon-based synthetic oil havingno polar groups, or a co-oligomer of ethylene and alpha-olefin or anethylene-propylene copolymer oil. Suitable oils include Lucant®,Parapol®, white mineral oil and other vegetable or mineral oils.

Other optional components include a low melting alloy such as Wood'smetal, Field's metal or other alloy which melts between about 35° C. andabout 180° C., between about 45° C. and about 100° C., or between about45° C. and about 60° C. One example of Field's metal is a fusible alloythat becomes liquid at approximately 62° C. (144° F.) and is a eutecticalloy of bismuth, indium, and tin, with the following percentages byweight: 32.5% Bi, 51% In, 16.5% Sn. A heat transfer material comprisinga low melting alloy may soften during normal operating conditions inorder to allow for the heat transfer material to flow across, and betterconform to, any surfaces through which heat transfer is desired.

In addition, antioxidants are optionally included in the heat transfermaterial to inhibit oxidation and thermal degradation of the phasechange system. The antioxidant may be phenol type or amine typeantioxidants, or any other suitable type of antioxidant, or acombination thereof. The phenol or amine type antioxidant may also be asterically hindered phenol or amine type antioxidant. For example, theantioxidant may be a phenol type antioxidant such as Irganox® 1076, oroctadecyl 3-(3,5-di-(tert)-butyl-4-hydroxyphenyl) propionate. In otherembodiments, the antioxidant may be an amine type antioxidant such asIrganox® 565, or2,6-di-tert-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino) phenol.The antioxidant may also be a sulfur containing phenolic antioxidant,for example a sterically hindered sulfur containing phenolicantioxidant. In some embodiments, thermally stable antioxidants from anyof the above types of antioxidants may be used. The heat transfermaterial may comprise from about 0.01 wt % to about 5 wt %, from about0.05 wt % to about 2 wt %, or from about 0.07 wt % to about 1.1 wt % ofantioxidant.

Other optional components may also be added to the heat transfermaterial. For example, crosslinking compounds or resins may be added tothe heat transfer material in order to give the heat transfer material adesired consistency. In some embodiments, amines or amine-based resinsare added or incorporated into the rubber composition or mixture ofrubber compounds, facilitating a crosslinking reaction between theamines or amine resins and primary or terminal hydroxyl groups on atleast one of the rubber compounds. The crosslinking reaction between theamine resin and the rubber compounds produces a “soft gel” phase in themixture instead of a liquid state. The degree of crosslinking betweenthe amine resin and the rubber composition and/or between the rubbercompounds themselves will determine the consistency of the soft gel. Forexample, if the amine resin and the rubber compounds undergo a minimalamount of crosslinking (10% of the sites available for crosslinking areactually used in the crosslinking reaction) then the soft gel will bemore “liquid-like”. However, if the amine resin and the rubber compoundsundergo a significant amount of crosslinking (40-60% of the sitesavailable for crosslinking are actually used in the crosslinkingreaction and possibly there is a measurable degree of intermolecular orintramolecular crosslinking between the rubber compounds themselves)then the gel would become thicker and more “solid-like”.

Amine resins are those resins that comprise at least one aminesubstituent group on any part of the resin backbone. Amine resins arealso synthetic resins derived from the reaction of urea, thiourea,melamine or allied compounds with aldehydes, particularly formaldehyde.Typical and contemplated amine resins are primary amine resins,secondary amine resins, tertiary amine resins, glycidyl amine epoxyresins, alkoxybenzyl amine resins, epoxy amine resins, melamine resins,alkylated melamine resins, and melamine-acrylic resins. Melamine resinsare particularly useful and preferred in several contemplatedembodiments described herein because a) they are ring-based compounds,whereby the ring contains three carbon and three nitrogen atoms, b) theycan combine easily with other compounds and molecules throughcondensation reactions, c) they can react with other molecules andcompounds to facilitate chain growth and crosslinking, d) they are morewater resistant and heat resistant than urea resins, e) they can be usedas water-soluble syrups or as insoluble powders dispersible in water,and f) they have high melting points (greater than about 325° C. and arerelatively non-flammable). Alkylated melamine resins, such as butylatedmelamine resins, are formed by incorporating alkyl alcohols during theresin formation. Other examples of cross-linking compounds and methodsare provided in U.S. Pat. No. 7,244,491, entitled “Thermal InterfaceMaterials,” which is incorporated herein by reference in its entirety.The heat transfer material may comprise less than about 5 wt %, lessthan about 2 wt %, or less than about 1 wt %, of crosslinking agent.

The wt % of the different components of the heat transfer material maybe any combination of the wt % ranges provided above. As one example,the heat transfer material has from about 5 wt % to about 10 wt % of thepolymeric elastomer material, from about 1 wt % to about 5 wt % of thewax or phase change material, from about 85 wt % to about 92 wt %thermally conductive filler, from about 0.07 wt % to about 1.1 wt %antioxidant, and from about 0.65 wt % to about 1.2 wt % coupling agent.Optionally, less than about 1 wt % of a cross-linking agent may also beadded to the heat transfer material. Other compounds in addition tothose listed above may be added to the heat transfer material, forexample any of the compounds provided in U.S. Pat. No. 6,451,422,entitled “Thermal Interface Materials,” U.S. Pat. No. 7,244,491,entitled “Thermal Interface Materials”, and U.S. Patent Publication No.2006/0040112, entitled “Thermal Interconnect and Interface Systems,Methods of Production and Uses Thereof,” all three of which areincorporated herein by reference in their entirety.

The heat transfer materials described herein may be prepared bycombining the polymeric elastomer component, the optional wax or otherphase change material, and the optional antioxidant. These componentsare blended and heated until the wax or other phase change materialand/or the polymeric elastomer components melt to form a first mixture.The coupling agent is then added to the mixer and blended with thecoupling agent to form a second mixture. The thermal filler material isthen added to the second mixture, either all in one step or in multiplesteps, and blended to form the final heat transfer material. In someembodiments of the present invention, in the finished heat transfermaterial, the thermal filler forms discrete domains within the polymericelastomer component, and as such, even with the addition of the couplingagent, the thermal filler is not homogeneously distributed throughoutthe polymeric elastomer component.

The heat transfer material may be used in the manufacture ofsubassemblies and/or electronic devices using a variety of techniques.For example, the heat transfer material may by formed into a series ofpads wherein the pads are formed between first and second liners. Thethickness of the pads may be approximately 10 mil, or between about 5and about 20 mil. The pads may be cut to a desired size before or afterbeing placed between the liner materials.

The heat transfer material may optionally be chilled prior toapplication to make it easier to handle and remove from the liners. Thesurface of a substrate that the heat transfer material will contact maybe cleaned (e.g., a semiconductor die and/or a heat spreader), forexample with IPA. The substrate is optionally heated, the first liner isremoved from the heat transfer material, and the heat transfer materialis applied to the substrate. The substrate may then be allowed to cooland the second liner is then removed. In embodiments in which the heattransfer material is to be placed between a heat spreader and asemiconductor die, the heat transfer material is applied to a firstsubstrate (i.e., one of the heat spreader or the semiconductor die) asdescribed above, and then the first substrate is applied to the secondsubstrate (i.e., the other of the heat spreader or the semiconductordie), essentially forming a sandwich with the heat transfer materialbetween the heat spreader and the semiconductor die, as shown in FIG. 1.

In another method according to some embodiments of the presentinvention, the heat transfer material is formed into a shape that can bedispensed, for example through a hot melt system. The heat transfermaterial is melted in the hot melt system, and dispensed onto a firstsubstrate (one of the semiconductor die or the heat spreader). Asmentioned above, the semiconductor die and the heat spreader are thenplaced together, essentially forming a sandwich with the heat transfermaterial disposed between the heat spreader and the semiconductor die,as shown in FIG. 1.

In yet another method according to some embodiments of the presentinvention, the heat transfer material is dissolved in a solvent, forexample an aliphatic hydrocarbon solvent such as cyclohexane, heptane,dodecane, a paraffinic oil, process oil or isoparaffin fluid, or othersuitable solvent. The solution is then applied to one or both of thesemiconductor die and the heat spreader using a screen printing process.The semiconductor die and the heat spreader are then placed together,essentially forming a sandwich with the heat transfer material disposedbetween the heat spreader and the semiconductor die, as shown in FIG. 1.

A number of different types of tests are available for testing theefficacy of a heat transfer material. For example, three examples ofsuch tests are a thermal cycling test, a Highly Accelerated Stress Test(HAST), and a bake test. These tests are typically run on samples ofheat transfer material that have been disposed between a heat spreadersubstrate and a semiconductor substrate. In one example of a thermalcycling test, the heat transfer material is cycled between −55° C. and125° C. 1000 times. This test is commonly referred to as the TC1000JEDEC B test. Typically, a thermocouple is affixed to the heat transfermaterial and the temperature of the heat transfer material is cycledcontinuously between the two temperatures (when one end of thetemperature range is reached, the system begins heating or cooling tothe other end of the temperature range). In one example of a HAST test,the heat transfer material is placed in 130° C., 85% RH conditions for96 hours (this is the full HAST test referred to in the followingexamples). In one example of a bake test, the heat transfer material isplaced in an oven at 125° C. or 150° C. for 1000 hours. In these tests,the heat transfer material is placed in a “sandwich” between asemiconductor material and a heat spreader material (e.g., a nickelcoated copper material).

In addition, heat transfer materials may also be tested in anabbreviated HAST test. In this test, the heat transfer materials areplaced in an open container (e.g., a lid or tray, typically on a heatspreader material such as a nickel-coated copper). Without beingincorporated into a sandwich structure discussed above, the material issubjected to the HAST conditions described above.

Upon completion of any of these tests, the heat spreader/heat transfermaterial/semiconductor substrate composite is examined for delaminationbetween the heat transfer material and the heat spreader and/or thesemiconductor substrate, or other physical defects. If no defects arefound, the material passes the test. The thermal performance (e.g.,thermal impedance and/or thermal conductivity) of the test sandwich mayalso be tested before and after any of these tests. In the abbreviatedHAST test, the heat transfer material is inspected for visual defectssuch as cracks or other deformities and the weight change of thematerial is also tested. If no defects are found, the material passesthe test.

The heat transfer properties of the heat transfer materials may also betested in a variety of ways. For example, a cut bar test may be used tomeasure thermal conductivity and thermal impedance. One example of a cutbar test is described in the ASTM D 5470-06 test method. When testingaccording to this method, at least some of the heat transfer materialsdescribed herein have a thermal conductivity of at least about 2.5 W/mK,or at least about 2.7 W/mK, at least about 3.0 W/mK, at least about 3.7W/mK, at least about 4.0 W/mK, or at least about 4.4 W/mK. Thermalimpedance is less than about 0.20 mm²·K/W at 50 micron thickness, lessthan about 0.16 mm²·K/W at 50 micron thickness, less than about 0.12mm²·K/W at 50 micron thickness, or less than about 0.10 mm²·K/W at 50micron thickness.

In addition, the thermal impedance and/or the thermal conductivity maybe tested before and after the reliability testing described above. Theamount of degradation in the thermal conductivity and/or impedance is anindication of relatively lower thermal performance. For example, thethermal impedance and/or conductivity of some of the heat transfermaterial embodiments described herein show 0%, less than about 5% orless than about 10% decrease in thermal conductivity (or increase inthermal impedance) subsequent to any of the above reliability testscompared to measurements taken prior to the reliability tests.

Further, the change in the weight of the heat transfer material may alsobe monitored before and after any of the above tests. In some cases, aweight change of less than about 10%, less than about 5%, less thanabout 2%, or less than about 1% may indicate that the heat transfermaterial is thermally stable and may be an effective heat transfermaterial for TIM1 and/or TIM2 applications.

The following examples are illustrative of a number of embodiments ofthe invention. (Note that all wt % values provided in the examples arebased on the finished weight of the TIM.)

Example 1

In example 1, 6.5 wt % Kraton® elastomer (a hydroxyl-terminated ethylenebutylene copolymer, specialty mono-ol), 1.9 wt % of a microcrystallinewax with a melting point of about 45° C., and 0.10 wt % Irganox® 1076were combined and blended in a heated mixer until the combination hadmelted and had a substantially homogeneous appearance. 0.7 wt % TitaniumIV 2,2 (bis 2-propenolatomethyl)butanolato, tris(dioctyl)pyrophosphato-Owas added, and the combination was blended, again until the combinationhad a substantially homogeneous appearance. 90.8 wt % of Aluminum powderwas added, and the combination was again blended until it had asubstantially homogeneous appearance. The coupling agent did not appearto be completely miscible with the combination of elastomer, wax andantioxidant.

The thermal interface material was then taped between liner films at 90°C. for 15 minutes, and cut to a 10 mm square. The liners were removedand the square sample placed between a nickel-coated copper spreader anda silicon die, creating a “test sandwich.” Thermal impedancemeasurements were made using flash diffusivity of the test sandwich.Netzsch LFA 447 equipment with a Xenon light source was used for thesemeasurements both before and after HAST testing. The test sandwich wassubjected to HAST conditions for 96 hours (HAST testing is described infurther detail below). This material passed HAST (there was nosignificant visible degradation of the TIM, and no delamination betweenthe TIM and the nickel-coated copper spreader or between the TIM and thesilicon die). In addition, the thermal performance did not significantlydegrade (testing for thermal performance is further described below).Specifically, the thermal impedance of the test sandwich was the sameafter HAST testing compared to before (both values were 0.09° C.·cm²/W).

Example 2

Example 2 was prepared according to the procedure described above withrespect to Example 1. The types and amounts of the different componentswere also the same as in Example 1, except that Zirconium IV 2,2 (bis2-propenolatomethyl)butanolato, tris(diisooctyl)pyrophosphato-O was usedin place of the Titanium IV 2,2 (bis 2-propenolatomethyl)butanolato,tris(dioctyl)pyrophosphato-O, and Honeywell low density polyethyleneA-C® 617 wax (a low-density, low molecular weight polyethylenehomopolymer having a Mettler Drop Point of 101° C. by ASTM D-3954 and anASTM D-5 hardness of 7.0 and a density of 0.91 g/cc by ASTM D-1505) wasused in place of the wax used in Example 1. The coupling agent did notappear to be completely miscible with the combination of elastomer, waxand antioxidant. This TIM was used to produce a test sandwich, asdescribed with respect to Example 1, and the test sandwich was subjectedto HAST conditions for 96 hours. The material passed HAST. In addition,the thermal performance did not significantly degrade. Specifically, thethermal impedance of the test sandwich was the same after HAST testingcompared to before (both values were 0.11° C.·cm²/W).

Example 3

Example 3 was prepared according to the procedure described above withrespect to Example 1. The types and amounts of the different componentswere also the same as in Example 1, except that the amount of Kraton was6.2 wt % and the amount of antioxidant was 0.50 wt %. In addition, thewax of Example 1 was replaced with 1.8 wt % Lucant® oil. The couplingagent did not appear to be completely miscible with the combination ofelastomer, oil and antioxidant. This TIM was prepared and tested asdescribed above with respect to Example 1. The test sandwich passedHAST, and the thermal impedance of the material actually decreased (thethermal impedance was 0.11° C.·cm²/W and after HAST testing and 0.10°C.·cm²/W after HAST testing).

Comparative Example 1

Comparative Example 1 was prepared according to the procedure describedabove with respect to Example 1. The types and amounts of the differentcomponents were the same as in Example 1 except that the followingcoupling agent was used in place of the coupling agent of Example 1:

Titanium IV, 2-propanolato, tris isooctadecanoato-O

In addition, 0.4 wt % of butylated melamine was also added and 90.4 wt %(rather than 90.8 wt %) of the filler was added. The coupling agentappeared to be substantially completely miscible with the combination ofelastomer, wax, antioxidant and butylated melamine. The material failedHAST. In addition, significant degradation in the thermal performancewas observed. Specifically, the thermal impedance of the test sandwichincreased from 0.10° C.·cm²/W to 0.50° C.·cm²/W).

The above examples illustrate that the coupling agents of the presentinvention provide a thermal interface material that passes HAST andprovides relatively consistent thermal performance before and after HASTtesting.

In addition, several of the coupling agents were tested in anabbreviated HAST testing.

Example 4

A TIM was produced according to Example 1 above and the TIM was spreadon a nickel-coated copper heat spreader at a thickness of 10 mil andexposed to HAST conditions for 96 hours. The material had a 0.4% gain inweight.

Example 5

A TIM was produced according to Example 2 above, and the TIM wasprepared and tested as described above with respect to Example 4. Thematerial had a 0.3% gain in weight.

Example 6

A TIM was produced according to Example 3 above, and the TIM wasprepared and tested as described above with respect to Example 4. Thematerial had a 0.7% gain in weight.

Example 7

A TIM was produced according to Example 2 except that Titanium IV,2-propanolato, tris(dioctyl)-pyrophosphato-O) adduct with 1 mole ofdiisooctyl phosphite was used in place of the Titanium IV 2,2 (bis2-propenolatomethyl)butanolato, tris(dioctyl)pyrophosphato-O. Thecoupling agent did not appear to be completely miscible with thecombination of elastomer, wax and antioxidant. This TIM was prepared andtested as described above with respect to Example 4. The material had a0.2% gain in weight.

Example 8

A TIM was produced according to Example 3 except that a microcrystallinewax with a melting point of about 45° C. (the same wax as in Example 1)was used in place of the Lucant® oil. The coupling agent did not appearto be completely miscible with the combination of elastomer, wax andantioxidant. This TIM was prepared and tested as described above withrespect to Example 4. The material had no change in weight.

Comparative Example 2

A TIM was produced according to Comparative Example 1 above. This TIMwas prepared and tested as described above with respect to Example 4.The material had a 20.4% gain in weight.

Comparative Example 3

A TIM was produced according to Example 1 except that Titanium IV,2-propanolato, tris isooctadecanoato-O coupling agent was used in placeof the coupling agent of Example 1. The coupling agent appeared to besubstantially completely miscible with the combination of elastomer, waxand antioxidant. This TIM was prepared and tested as described abovewith respect to Example 4. The material had a 20.7% gain in weight.

These abbreviated HAST tests described in Examples 4-8 and comparativeexamples 2 and 3 show that formulations that pass the full HAST testingand have good stability in thermal performance after being subjected tothe full HAST testing also have a relatively small change in weight whentested in the abbreviated HAST test. In addition, these abbreviated HASTtests illustrate that different TIM formulations of the presentinvention also have a relatively low weight loss and/or degradation inthermal performance after abbreviated HAST testing.

The following examples 9-14 and comparative examples 4 and 5 weresubjected to full HAST testing:

Example 9

In example 9, 6.22 wt % Kraton® elastomer (a hydroxyl-terminatedethylene butylene copolymer, specialty mono-ol), 1.78 wt % of amicrocrystalline wax with a melting point of about 45° C., and 0.5 wt %Irganox® 1076 were combined and blended in a heated mixer (the mixer hada heating jacket and the heating oil was maintained at 140° C.) untilthe combination had melted and had a substantially homogeneousappearance. 0.67 wt % Titanium IV 2,2 (bis2-propenolatomethyl)butanolato, tris(dioctyl)pyrophosphato-O was added,and the combination was blended at an oil temperature of 140° C., againuntil the combination had a substantially homogeneous appearance. 90.8wt % of Aluminum powder was added, and the combination was again blendedat an oil temperature of 140° C. until it had a substantiallyhomogeneous appearance, forming a heat transfer material. The couplingagent did not appear to be completely miscible with the combination ofelastomer, wax and antioxidant.

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.098° C. cm²/W. After HAST, thermalimpedance was 0.077° C. cm²/W. Thermal conductivity was 3.26 W/mK priorto HAST and 4.131 W/mK after HAST.

Example 10

In Example 10, a heat transfer material was produced according to themethod described in Example 9 except Zirconium IV 2,2 (bis2-propenolatomethyl)butanolato, tris(diisooctyl)pyrophosphato-O couplingagent was used in place of the coupling agent used in Example 9.However, when an attempt was made to spread this heat transfer materialbetween a silicon die and a heat spreader, the viscosity of the heatspreader material was too high to form an effective sandwich, and thismaterial was not tested. Rather, the heat transfer material was producedagain according to the method described in Example 9 except the oiltemperatures were 120° C. rather than 140° C. The lower temperatureresulted in a lower dynamic viscosity of 161 Pa·s compared to 205 Pa·sat the higher temperature (viscosity was measured using cone and plate(1 degree cone) geometry in a Haake RT20 rheometer at 87° C. andreported at 25 Hz.

The heat transfer material that was produced at the lower temperaturewas disposed between a silicon die and a nickel coated heat spreader andsubjected to full HAST testing. The thermal impedance prior to HAST was0.108° C. cm²/W. After HAST, thermal impedance was 0.106° C. cm²/W.Thermal conductivity was 3.41 W/mK prior to HAST and 3.478 W/mK afterHAST.

This example illustrates that some properties of heat transfer materialsthat contain certain coupling agents may be affected by processingconditions such as temperature. Specifically, in some embodiments theprocessing conditions of any of the heat transfer materials describedherein may be adjusted to ensure that the dynamic viscosity of the heattransfer material is less than 200 Pa·s, less than 180 Pa·s, less than170 Pa·s or less than 160 Pa·s. For example, the temperature of theheating medium may be maintained below 140° C., at or below 130° C., orat or below 120° C.

Example 11

In Example 11, a heat transfer material was produced according to themethod described in Example 9 except Titanium IVbis(diisooctyl)pyrophosphato-O, ethylenediolato, (adduct), bis(dioctyl)(hydrogen)phosphite coupling agent was used in place of the couplingagent used in Example 9.

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.107° C. cm²/W. After HAST, thermalimpedance was 0.105° C. cm²/W. Thermal conductivity was 3.515 W/mK priorto HAST and 3.588 W/mK after HAST.

Example 12

In Example 12, a heat transfer material was produced according to themethod described in Example 9 except Titanium IV, 2-propanolato,tris(dioctyl)-pyrophosphato-O) adduct with 1 mole of diisooctylphosphite coupling agent was used in place of the coupling agent used inExample 9.

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.099° C. cm²/W. After HAST, thermalimpedance was 0.073° C. cm²/W. Thermal conductivity was 3.265 W/mK priorto HAST and 4.411 W/mK after HAST.

Example 13

In Example 13, a heat transfer material was produced according to themethod described in Example 9 except Titanium IVbis(dioctyl)pyrophosphato-O, oxoethylenediolato, (adduct), bis(dioctyl)(hydrogen)phosphite-O coupling agent was used in place of the couplingagent used in Example 9.

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.098° C. cm²/W. After HAST, thermalimpedance was 0.088° C. cm²/W. Thermal conductivity was 3.189 W/mK priorto HAST and 3.551 W/mK after HAST.

Example 14

In Example 14, a heat transfer material was produced according to themethod described in Example 9 except (Zirconium IV2,2-bis(2-propenolatomethyl) butanolato, cyclo di[2,2-(bis2-propenolatomethyl)butanolato], pyrophosphato-O,O) coupling agent wasused in place of the coupling agent used in Example 9.

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.107° C. cm²/W. After HAST, thermalimpedance was 0.098° C. cm²/W. Thermal conductivity was 3.262 W/mK priorto HAST and 3.566 W/mK after HAST.

Comparative Example 4

In Comparative Example 4, a heat transfer material was producedaccording to the method described in Example 9 except Titanium IV,2-propanolato, tris isooctadecanoato-O coupling agent was used in placeof the coupling agent used in Example 9.

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.108° C. cm²/W. After HAST, thermalimpedance was 0.204° C. cm²/W. Thermal conductivity was 3.403 W/mK priorto HAST and 1.924 W/mK after HAST.

This Comparative Example was also produced at a lower temperature of120° C. Samples produced at this lower temperature were disposed betweena silicon die and a nickel coated heat spreader and subjected to fullHAST testing. The thermal impedance prior to HAST was 0.109° C. cm²/W.After HAST, thermal impedance was 0.365° C. cm²/W. Thermal conductivitywas 3.515 W/mK prior to HAST and 1.196 W/mK after HAST. Because theresults at both temperatures were similar, the thermal impedance and thethermal conductivity do not appear to be affected by changes in thetemperature within this temperature range.

Comparative Example 5

In Comparative Example 5, a heat transfer material was producedaccording to the method described in Example 9 except that the followingcoupling agent was used:

Titanium IV, 2,2 (bis 2-propenolatomethyl)butanolato, trisneodecanoato-O:

The heat transfer material was disposed between a silicon die and anickel coated heat spreader and subjected to full HAST testing. Thethermal impedance prior to HAST was 0.131° C. cm²/W. After HAST, thermalimpedance was 0.263° C. cm²/W. Thermal conductivity was 3.769 W/mK priorto HAST and 1.921 W/mK after HAST.

Examples 9-14 and Comparative Examples 4 and 5 show that heat transfermaterials of the present invention exhibit acceptable and stable thermalproperties when compared to heat transfer materials produced accordingto Comparative Examples 4 and 5.

The invention claimed is:
 1. A heat transfer material comprising: about3 wt. % to about 14 wt. % of a polymeric elastomer material; a wax,wherein the wax comprises less than about 10 wt. % of the heat transfermaterial; about 80 wt. % to about 95 wt. % of a thermally conductivefiller; and about 0.3 wt. % to about 2 wt. % of a coupling agentselected from the group consisting of: titanium IV 2,2 (bis2-propenolatomethyl)butanolato, tris(dioctyl)pyrophosphato-O; zirconiumIV 2,2 (bis 2-propenolatomethyl)butanolato,tris(diisooctyl)pyrophosphato-O; titanium IVbis(dioctyl)pyrophosphato-O, oxoethylenediolato, adduct, bis(dioctyl)(hydrogen)phosphite-O; and zirconium IV2,2-bis(2-propenolatomethyl)butanolato, cyclo di[2,2-(bis2-propenolatomethyl)butanolato], pyrophosphato-O,O.
 2. The material ofclaim 1, wherein the polymeric elastomer material comprises hydrogenatedpolybutadiene.
 3. The material of claim 1, wherein the thermallyconductive filler comprises particles of a metal selected from the groupconsisting of: silver, aluminum, copper and alloys thereof.
 4. Thematerial of claim 3, wherein the thermally conductive filler comprisesparticles of aluminum.
 5. The material of claim 1, wherein the couplingagent is titanium IV 2,2 (bis 2-propenolatomethyl)butanolato,tris(dioctyl)pyrophosphato-O.
 6. The material of claim 5, wherein thematerial comprises from about 0.5 wt. % to about 1 wt. % of the couplingagent.
 7. The material of claim 5, wherein the material comprises fromabout 0.5 wt. % to about 0.7 wt. % of the coupling agent.
 8. Thematerial of claim 5, wherein the material comprises: from about 5 wt. %to about 10 wt. % of the polymeric elastomer material; from about 1 wt.% to about 5 wt. % of the wax; from about 85 wt. % to about 92 wt. % ofthe thermally conductive filler; and from about 0.5 wt. % to about 1 wt.% of the coupling agent.
 9. The material of claim 5, wherein the polymerelastomer material comprises a material selected from the groupconsisting of: an ethylene-propylene rubber, a polyethylene/butylene, apolyethylene-butylene-styrene, a polyethylene-propylene-styrene, ahydrogenated polyalkyldiene mono-ol, a hydrogenated polyalkyldiene diol,a hydrogenated polyisoprene, polyolefin elastomer, and blends thereof.10. The material of claim 5, wherein the polymer elastomer materialcomprises a hydrogenated polybutadiene mono-ol.
 11. The material ofclaim 5, further comprising an amine resin that is crosslinkable withthe polymeric elastomer material.
 12. The material of claim 1, whereinthe coupling agent is zirconium IV 2,2 (bis2-propenolatomethyl)butanolato, tris(diisooctyl)pyrophosphato-O.
 13. Thematerial of claim 1, wherein the coupling agent is titanium IVbis(dioctyl)pyrophosphato-O, oxoethylenediolato, adduct, bis(dioctyl)(hydrogen)phosphite-O.
 14. The material of claim 1, wherein the couplingagent is zirconium IV 2,2-bis(2-propenolatomethyl)butanolato, cyclodi[2,2-(bis 2-propenolatomethyl)butanolato], pyrophosphato-O,O.
 15. Thematerial of claim 1, further comprising a phenolic antioxidant.
 16. Thematerial of claim 1, wherein the wax comprises a polymer wax selectedfrom polyethylene waxes, polypropylene waxes, and copolymers thereof.17. The material of claim 16, wherein the wax comprises a polyethylenehomopolymer.
 18. The material of claim 1, further comprising an amineresin that is crosslinkable with the polymeric elastomer material. 19.The material of claim 18, wherein the amine resin and the polymericelastomer material are crosslinked at 10% of sites available forcrosslinking to produce a liquid-like soft gel.
 20. The material ofclaim 18, wherein the amine resin and the polymeric elastomer materialare crosslinked at 40-60% of sites available for crosslinking to producea solid-like soft gel.
 21. The material of claim 18, wherein thematerial comprises: from about 5 wt. % to about 10 wt. % of thepolymeric elastomer material; from about 1 wt. % to about 5 wt. % of thewax; from about 85 wt. % to about 92 wt. % of the thermally conductivefiller; from about 0.5 wt. % to about 1 wt. % of the coupling agent;from about 0.07 wt. % to about 1.1 wt. % of a phenolic antioxidant; andless than about 1 wt. % of the amine resin.
 22. The material of claim18, wherein the amine resin is an alkylated melamine.
 23. The materialof claim 1, wherein the polymer elastomer material comprises a materialselected from the group consisting of: an ethylene-propylene rubber, apolyethylene/butylene, a polyethylene-butylene-styrene, apolyethylene-propylene-styrene, a hydrogenated polyalkyldiene mono-ol, ahydrogenated polyalkyldiene diol, a hydrogenated polyisoprene,polyolefin elastomer, and blends thereof.
 24. The material of claim 1,wherein the polymer elastomer material comprises a hydrogenatedpolybutadiene mono-ol.